cc: Fix BytesPerPixel issue and refactor.

cc/resources/resource_provider.cc

Index: cc/resources/resource_provider.cc
diff --git a/cc/resources/resource_provider.cc b/cc/resources/resource_provider.cc
index f081f6236f87a36410537af4a9c0e570f1191510..2a8220aa2ac56fb88add919d40531ca1ef41299f 100644
--- a/cc/resources/resource_provider.cc
+++ b/cc/resources/resource_provider.cc
@@ -1524,12 +1524,15 @@ void ResourceProvider::AcquirePixelBuffer(ResourceId id) {
     resource->gl_pixel_buffer_id = buffer_id_allocator_->NextId();
   gl->BindBuffer(GL_PIXEL_UNPACK_TRANSFER_BUFFER_CHROMIUM,
                  resource->gl_pixel_buffer_id);
-  unsigned bytes_per_pixel = BitsPerPixel(resource->format) / 8;
-  gl->BufferData(
-      GL_PIXEL_UNPACK_TRANSFER_BUFFER_CHROMIUM,
-      resource->size.height() *
-          MathUtil::RoundUp(bytes_per_pixel * resource->size.width(), 4u),
-      NULL, GL_DYNAMIC_DRAW);
+
+  base::CheckedNumeric<int> num_bytes = resource->size.height();

[reveman, 2015/06/24 18:02:26]

why CheckedNumeric?

+  int bytes_per_row_aligned =

[reveman, 2015/06/24 18:02:26]

How about just bytes_per_row and round up to multiple of 4 in the call below as
before?

+      (resource->size.width() * BitsPerPixel(resource->format)) / 8;
+  bytes_per_row_aligned = MathUtil::RoundUp(bytes_per_row, 4u);
+  num_bytes *= bytes_per_row_aligned;
+
+  gl->BufferData(GL_PIXEL_UNPACK_TRANSFER_BUFFER_CHROMIUM,
+                 num_bytes.ValueOrDie(), NULL, GL_DYNAMIC_DRAW);
   gl->BindBuffer(GL_PIXEL_UNPACK_TRANSFER_BUFFER_CHROMIUM, 0);
 }